Refrigerating apparatus



Sept. 15, 1931. F. w. ANDREWS REFRIGERATING APPARATUS Filed March 31, 1927 2 Sheets-Sheet l p 1931- F. w. ANDREWS 1,823,079

' REFRIGERATING APPARATUS v Filed-March 5 1, 1927 2 Sheets-Sheet 2 Jfi I II I H I ll a: ll H ,1'

Patented Sept. 15, 1931 i I 1,823,079

UNITED STATES PATENT OFFICE FRANK W. ANDREWS, F DAYTON, OHIO, ASSIGNOR, BY MESNE ASSIGNMENTS, TO FRIGIDAIRE CORPORATION, A CORBORATION' OF DELAWARE REFRTGERATING APPARATUS Applicatio'ii filed March 31, 1927. Serial No. 179,983.

This invention relates to evaporators for large heat transfer surface. This is usually refrigerating apparatus and is particularly effected by providing the evaporator with a tiseful in refrigerating cabinets of the houselarge number of conduits. Butthis arrangehold type. a ment is open to two objections: first, a large It is among the objects of the invention to number of joints between conduits and the 55 provide an improved evaporator having a header makes ahigh manufacturing cost and relatively large heat transfer surface in consecond, the volume of refrigerant which tact with a relatively small volume of resuch an arrangement contains may be objecfrigerant; to provide an evaporator having tionally large. This is true particularly in a large holdover capacity; and to generally the case of units of large capacity where 10- 60 simplify and improve the construction of cal ordinances or shipping regulations limit evaporators of this type. the quantity of refrigerant which may be In the drawings: placed in any one unit. Figs. 1 and 2 are front and side elevations In accordance with my invention I reduce respectively, partly in section, of one form the quantity of refrigerant which is neces- 65 of evaporator embodying my invention; .sary in a given evaporator without appreci- Fig. 3 is an enlarged section of a portion ably reducing the heat transfer area by fillof the evaporator shown in Figs. 1 and 2; ing some or all of the conduits with granular Fig. 4 is an end elevation partly in section material, indicated in the drawings by 16.

go of a modified form of evaporator; and The granules considerably reduce the free 70 Fig. 5 1s a side elevation partly 1n section volume of the conduits, that is, the volume of the evaporator shown in Fig. 4. which may contain refrigerant, the space be- Referring to the drawings, 10 indicates a tween the granules being able to contain all header forming a reservoir for liquid rethe refrigerant which can be evaporated by frigerant which is admitted thereto thru a the heat transferred thru the walls of the 7 conduit connection 11 under the control of conduits. If the granular material is irrega float valve 12. Connected to the header ular such as sharply broken stone or the are a number of refrigerant circulating conlike, it will be in contact with the surfaces duits 13 for cooling a surrounding medium of the tubes only at sharp points or corners for example air, and which as shown in the and thusthe presence of the granular inaso drawings, are slender pipes or tubes formed terial will not appreciably reduce the amount into loops. The loops may be formed in of surface in contact with the refrigerant. the manner of a figure 8 to form enclosures I may use any material of proper size to for brine tanks 14 which in turn form 611- take up the desired space, such as crushed closures for ice making pans 15. Liquid restone or metallic scraps or punchings, shot, 35 frigerant is supplied to the evaporator by or the like. However, I prefer to use a subany suitable refrigerating apparatus, for stance having high specific heat, such as example, as described in the patent to Joy, granite, in order to provide a storage or 1,367,266, February 1, 1921. The liquid is holdover for the evaporator in case the rekept at a constant level in the header and frigerating system should be temporarily out evaporates in the tubes producing refrigeraof operation. tion in the well known manner. The presence in the refrigerant ducts of The rapidity with which the refrigerant this broken granular material having a mulevaporates, and conseq en y he m u t of titude of sharp corners, points, and projec- 45 heat which can be absorbed from the urtions has another important advantage. In rounding medium by a given evaporator, decooling units of the flooded type, much pends upon the area of the surface available trouble is had with oil logging. Lubricant for the transfer of heat between medium is carried from the compressor by the reand the refrigerant. Therefore tov have frigerant and is carried to theevaporator.

50 large capacity, an evaporator should have a The lubricant is ordinarily somewhat soluble in the liquid refrigerant. When the liquid refrigerant vaporizes it leaves most of the lubricant behind and some of the lubricant floats on top of the liquid refrigerant in the header and some of the lubricant tends to collect in the horizontal portions of the refrigerant ducts connected tothe header. The presence of this lubricant retards the formation of bubbles of gaseous refrigerant due .to the capillary effect of the lubricant and thus retards the evaporation of the liquid refrigerant in the ducts. This retardation of evaporation lowers the capacity of the cooling unit since it causes the duct to be kept at a higher temperature and also lowers the efficiency since a lower back pressure must be maintained in order to provide the required amountof refrigeration.

It has been found that minute bubbles of gaseoue refrigerant tend to form upon the sharp points, projections, and corners which are submerged 1n the llqllld refrigerant.

This aids evaporation in my refrlgerant both the efliciency cooling unit. The upon the sharp within the refrigerant ducts, grow larger and then leave the projections on which they have formed and rise through the refri erant ducts into the header'and carry the s ugs of lubricant along in to the header. This continuous bombardment of the bubbles has a tendency ducts and thus increases and the ca acity of the small bubb es, which form to break up the capillary effect in the ducts entirely b stirand sometimes prevents it ring the lubricant with the liquid re rigerant. Because of the multitude of sharp 4 points, projections and corners and the-revented from rising until moval of the capillary effect, the formation of the bubbles is continuous and not spasmodic. preventing the oil logging, capacity of the cooling unit is further increased. Another feature which assistsmaterially in bringing the lubricant slugs to the header is the fact that the horizontal portions of the refrigerant ducts tend to hold the bubbles until they grow to a larger size than they in a vertical porformmg The bubbles are thus rethey have reac ed a large size and these large bubbles are more effective to carry the lubricant slugs up into would reach if tion of the duct.

the header than are the small bubbles, which would form if the granular material were only the vertical ortions of the ducts. Thus the horizontal portions of the ducts, together with the multitude of sharp points,

corners and edges on the granular material form effective means for removing the lubri-- cant from the refrigerant ducts.

In Fig. 4 I have shown a modified form of evaporator in which there is a single narrow conduit 20 for circulating refrigerant By removing the lubricant and thus the efiiciency and used in any refrigerating system in which evaporators of this type are ordinarily suitable for example, household cabinets as described in the application of Jesse G. King, S. N. 149,745, filed November 20, 1926.

While the forms of embodiment of the present invention as herein disclosed, constitute preferred forms, stood that other forms all coming within the which follows.

What is claimed is as follows:

An evaporator comprising header means, a plurality of ducts connected in parallel circuit relation and containing liquidrefrigmight be'adopted, scope ,of the claim erant and having ends thereof connected with the header aneans for discharging vaporized refrigerant thereto, portions of said ducts beneath the normal level of the liquid lying substantially horizontal, and

means withln the ducts for accelerating the formation of gas bubbles in said ducts, said means comprising material havin ity of sharp corners on which sald bubbles will readily form.

In testimony whereof I hereto afiix my signature. I

the outsi e of the conit is to be undera plural- FRANKWIANDREWS. Y 

